<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>

        .box{
            width: 300px;
            height: 200px;
            background-color: pink;
        }

        .item{
            float: left;
            width: 76px;
            height: 196px;
            background-color: orange;
            border: 2px solid #333;
        }

        .item.active{
            /* margin-left: -10px; */
            /* margin-right: -10px; */

        }


        /* 合并边框的技巧 */
        /* .item+.item{
            border-left: none;
        } */
    </style>
</head>
<body>
    <div class="box">
        <div class="item">

        </div>
        <div class="item active">
            
        </div>
        <div class="item">
            
        </div>
    </div>
</body>
</html>